Recently, therapeutic treatments become possible by an ultrasonic endoscope not only for a digestive tract wall but also for a lesion in a pancreas or hepar, which is a substantial organ located deeper than the digestive tract wall. When an organ located deeper than the digestive tract wall is to be given therapeutic treatment, various medical technologies are used.
The medical technologies include a radio-frequency cautery treatment including a high-frequency cautery treatment, ablation technology such as cryotherapy, radiotherapy in which a radioactive isotope is embedded in a body, radiotherapy for treatment by radiation from outside the body and the like. In the radiotherapy in which radiation is applied from outside the body, a metal piece is indwelled in the body as a mark for positioning a lesion in an X-ray image.
In these medical technologies, a radio-frequency cautery treatment instrument or a marking member for radioactive treatment is used as a medical device. When such a medical device is guided into an organ to be treated, a puncture needle is used as the simplest way. In this case, first, a hollow puncture needle is stuck into a target portion of the organ. Next, a medical device is inserted into a through hole of the puncture needle and guided to a distal end of the puncture needle. However, it is extremely difficult to form a medical device with a small diameter so that the device can be inserted into the through hole with a small diameter of the puncture needle. If the puncture needle is made with a large diameter in order to facilitate insertion of the medical device, nonconformities such as lowered inserting capability of the puncture needle into a treatment instrument insertion channel, damage of the treatment instrument insertion channel by the puncture needle with a large diameter or deteriorated puncturing performance into an organ are worried about.
In Japanese Unexamined Patent Application Publication No. 2000-139944, for example, a radio-frequency cautery treatment instrument having excellent insertion maneuverability without damage on the treatment instrument insertion channel and smaller invasion into a patient is proposed. This radio-frequency cautery treatment instrument comprises a sheath portion to be inserted into a body cavity, a needle-state main body inserted into the sheath portion, projecting to the front from the distal end of the sheath portion, and capable of puncture into a living tissue portion, a first electrode arranged in the vicinity of the distal end portion of the sheath portion, and a second electrode provided at the distal end of the needle-state main body and separated from the first electrode. In the radio-frequency cautery treatment instrument, a bipolar electrode comprises the first electrode in the vicinity of the sheath portion distal end and the second electrode at the distal end of the needle-state main body. In a treatment using the radio-frequency cautery treatment instrument, the first electrode of the sheath portion is brought into contact with the surface of a lesion and the second electrode of the needle-state main body is stuck into the lesion. After that, the lesion is cauterized by having a radio-frequency current flown between the electrodes.
On the other hand, in Japanese Unexamined Patent Application Publication No. 2001-120558, a marking device for endoscope for detaining a marking member at a target portion in a body cavity is proposed. This marking device for endoscope comprises a hollow and lengthy catheter, a tapered needle-state puncture portion formed at the distal end of the catheter, a marking member accommodated capable of being pushed out of the puncture portion of the catheter and detained in a living tissue, a hollow pusher slidably inserted into the catheter and pushing-out and operating the marking member from the puncture portion toward the outside of the catheter, and a guide needle slidably provided in the hollow body of the pusher. At the puncture portion of the catheter, a slit is provided so that the catheter can be elastically deformed easily when the marking member is pushed out. The puncture portion of the catheter is stuck into a living tissue and the marking member accommodated in the catheter is pushed out by the pusher while being guided by the guide needle. By this operation, the marking member accommodated in the puncture portion of the catheter is detained at the target portion of the living tissue.
However, in the radio-frequency cautery treatment instrument proposed in the above Japanese Unexamined Patent Application Publication No. 2000-139944, the first electrode of the sheath portion is brought into contact with the gastric wall surface and the second electrode of the needle-state main body is stuck into the lesion close to the gastric wall from the gastric wall so as to carry out the radio-frequency cautery, for example. In this case, the radio-frequency cautery treatment is effective for the lesion in the vicinity of the gastric wall but not suitable for the cautery treatment for a lesion of an organ located at the depth of the gastric wall. That is because when the second electrode of the needle-state main body is stuck into the vicinity of the lesion of an organ located at the depth of the gastric wall for the radio-frequency cautery, a radio-frequency current is applied between the first electrode of the gastric wall surface and the second electrode stuck into the vicinity of the lesion so as to carry out the radio-frequency cautery also for the living tissue other than the lesion located between the first electrode and the second electrode.
That is, the radio-frequency cautery treatment instrument is suitable for the cautery treatment for a lesion in the vicinity of a digestive tract wall but not suitable for the cautery treatment for a lesion of an organ located deeper than the digestive tract wall.
On the other hand, the marking device for endoscope in Japanese Unexamined Patent Application Publication No. 2001-120558 is to detain the marking member at a target portion of a living tissue. Therefore, there is no suggestion at all that the radio-frequency cautery treatment instrument is inserted into a lesion of an organ located deeper than a digestive tract wall.
The present invention was made in view of the above circumstances and has an object to provide a medical treatment device capable of puncture a lesion of an organ at the depth of a body cavity so as to enable the radio-frequency cautery treatment only for the lesion.